Apparatus for controlling the field intensity in material processed in a capacitive high frequency field

ABSTRACT

A plurality of auxiliary electrodes positioned between material being processed in a capacitive high frequency field and between a high potential electrode and a grounded electrode permit the control of the field intensity in such material.

United States Patent [1 1 Grassmann et a].

[ 51 June 20, 1972 [54] APPARATUS FOR CONTROLLING THE [56] FIELD INTENSITY IN MATERIAL References Cited PROCESSED IN A CAPACITIVE HIGH UNITED STATES PATENTS FREQUENCY FIELD 2,479,351 8/1949 Hagopian .....219/ 10.81 X 2,504,956 4/1950 Atwood ..2l9/10.73 lnvemom "ans-Christian Gremlin", lselsdolf; 2,737,569 3/1956 Brown et a1... ....219/1o.s1 x Emil Walther, Erlansen. both of Germany 3,329,796 7/1967 Manwaring ....219/10.s1 x i Siemens Akflengeseuscha, Berlin and 3,404,462 10/1968 Hanson et al. ....219/l0-.8l X

Munich, Germany Primary Examiner-R. F. Staubly Filed: March 1970 Assistant Examiner-Hugh D. .laeger AppL No; 17,175 Attomey-Curt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel J. Tick Foreign Application Priority Data 57 ABSTRACT March 1969 Germany 19 12 9294 A plurality of auxiliary electrodes positioned between material being processed in a capacitive high frequency field and U.S. Cl ..219/l0.8l, 219/ 10.69, 219/1071 between a high potential electrode and a grounded electrode Int. Cl. ..H05b 9/04 permit the comm] fth fi ld intensity in such materiaL Field ofSearch ..219/10.81,10.69,10.71

9 Claims, 8 Drawing Figures APPARATUS FOR CONTROLLING THE FIELD INTENSITY IN MATERIAL PROCESSED IN A CAPACITIVE HIGH FREQUENCY FIELD DESCRIPTION OF THE INVENTION The invention relates to the control of the field intensity in material being processed. More particularly, the invention relates to apparatus for controlling the field intensity in material being processed in a capacitive high frequency field. The material being processed is positioned between a high potential electrode and a grounded electrode.

Many varied types of materials may be processed in a high frequency alternating field. The materials are either to be dried by expelling the moisture, or they are to contain another chemical compound by heating. During this and similar processes, a problem frequently arises during the placing of the material in the high frequency field, for example. The material being processed is subjected for a period of time to field intensities which are too high and produce an evaporation rate which is too high. It has been found, for example, that during the processing of textile coils or windings, the relatively high vapor pressure causes the individual windings or entire layers to be shifted. This results in considerable difficulties during the manufacturing process, particularly during the unwinding process. Furthermore, the sudden steam jet results in the formation of condensed water at the protective potential lids and even at the winding. This is a considerably detrimental influence on the quality of the goods being processed.

It is known to influence the field intensity by connecting ad ditional capacitances or inductances, or both, along one or more of the processing electrodes. This is disclosed in German Patent No. 895,955. It is also known to vary the field intensity by spacing the field electrodes at different distances from each other or by positioning the field electrodes at a more or less pointed angle relative to each other. This is disclosed in German Patent No. 917,385.

The aforedescribed arrangements for controlling the field intensity are detrimental and do not produce the desired results. This is due to the fact that they either require too much additional technical structure such as, for example, when the electrodes are placed obliquely, or they provide only limited variations in the field intensity. Limited variations in the field intensity very often are insufficient and are therefore not utilized in existing equipment, due to the deficiency of space.

Contrary to the known arrangements controlling the field intensity, the apparatus of our invention functions to adjust or control the field intensity in accordance with all the requirements relating thereto and is locally variable over the entire length of the furnace in which it is installed. The apparatus of the invention utilizes known components which may be subsequently installed in existing high frequency furnace equipment and may be removed rapidly and with facility. Furthermore, the apparatus of the invention utilizes simple components which filllCIlOl'l reliably and economically.

The principal object of the invention is to provide new and improved apparatus for controlling the field intensity in material being processed in a capacitive high frequency field.

An object of the invention is to provide apparatus of simple structure for controlling the field intensity in material being processed in a capacitive high frequency field.

An object of the invention is to provide apparatus for controlling the field intensity in material being processed in a capacitive high frequency field with efficiency, effectiveness, reliability and economy.

In accordance with the invention, apparatus for controlling the field intensity in material being processed in a capacitive high frequency field between a high potential electrode and a grounded electrode comprises auxiliary electrode means positioned between the material being processed and the high potential electrode.

The auxiliary electrode means comprises a plurality of auxiliary electrodes. Some of the auxiliary electrodes are at ground potential. Some of the auxiliary electrodes are insulated from the others.

A furnace houses the high potential electrode, the grounded electrode, the auxiliary electrodes and the material to be processed and has a longitudinal axis. The auxiliary electrodes are rods positioned either transversely or parallel to the longitudinal axis of the furnace or are tubes positioned either transversely or parallel to the longitudinal axis of the furnace, or are plates.

The high potential electrode has a specific width and the auxiliary electrodes are positioned transversely to the longitudinal axis of the furnace and each of the auxiliary electrodes has a length which is greater than the width of the high potential electrode. The auxiliary electrodes are parallel to each other. The auxiliary electrodes are rods having circular crosssectional areas, or rods having elliptical cross-sectional areas, or plates having angular cross-sectional areas with rounded edges. Each of the auxiliary electrodes is rotatable about one of its axes.

A mounting arrangement mounts the auxiliary electrodes in a manner whereby the distance between adjacent auxiliary electrodes is variable and the distance of the auxiliary electrodes from the grounded electrode is variable.

The high potential electrode and/or the auxiliary electrodes are heatable.

Some of the auxiliary electrodes are at ground potential if a reduced field intensity is desired at a specific locality. If, on the other hand, an increase in field intensity is desired in a specific locality, some of the auxiliary electrodes are insulated from the others.

It is desirable to heat the high potential electrode and/or the auxiliary electrodes in order to avoid the formation of condensed water. Each of the auxiliary electrodes is rotatable about one of its axes, when the cross-sectional area of each auxiliary electrode is elliptical or of plate configuration, in order to provide a precise adjustment or control of the field intensity.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of an embodiment of the apparatus of the invention;

FIG. la is a graphical presentation of the field intensity versus the length of the furnace housing the apparatus of the invention, when said apparatus is not utilized;

FIG. lb is a graphical presentation of the field intensity versus the length of the furnace housing the apparatus of the invention, when the auxiliary electrodes of the invention are grounded;

FIG. 10 is a graphical presentation of the field intensity versus the length of the furnace housing the apparatus of the invention, when some of the auxiliary electrodes of the invention are grounded and at least one of the auxiliary electrodes is insulated;

FIG. 2 is a schematic end view of the embodiment of FIG. 1;

FIG. 3 is a schematic diagram of a mounting arrangement of the apparatus of the invention;

FIG. 4 is a schematic diagram of an elliptical cross-sectional area of an auxiliary electrode of the invention; and

FIG. 5 is a perspective view of a plate-shaped embodiment of an auxiliary electrode of the invention.

In the FIGS., the same components are identified by the same reference numerals.

The high frequency furnace of FIG. 1 comprises a high potential electrode 1 which is electrically connected to a high frequency generator 2. A grounded transport belt 3 functions as the other electrode and moves the material to be processed through the high frequency field produced between itself and the high potential electrode 1. The material to be processed, for the purposes of illustration, comprises a plurality of spools, spindles, or spinning cakes 4a, 4b, 4c (FIG. 1), 4d, 4e (FIG. 2), and so on. At both base ends of each of the spools 4a, 4b, 4c, 4d, 4e, and so on, a corresponding insulating disc and a corresponding equipotential lid are provided in known manner.

The spool 4a has an insulating disc 5a on its top base, an insulating disc 5b on its bottom base, an equipotential lid 6a on its insulating disc 5a and an equipotential lid 6b on its insulating disc 5!). The spool 4b has an insulating disc 50 on its top base, an insulating disc 5d on its bottom base, an equipotential lid 6c on its insulating disc 5c and an equipotential lid 6d on its insulating disc 5d. The spool 40 has an insulating disc 5e on its top base, an insulating disc 5]" on its bottom base, an

equipotential lid 6e on its insulating disc 5e and an equipotential lid 6f on its insulating disc 5f. The spool 4d has an insulating disc 5 on its top base, an insulating disc 5h on its bottom base, an equipotential lid 6w on its insulating disc 5g and an equipotential lid 6 x on its insulating disc 5h. The spool 4e has an insulating disc 5i on its top base, an insulating disc Sj on its bottom base, an equipotential lid 6y on its insulating disc 5i and an equipotential lid 62, on its insulating disc 5j.

The spools, with their corresponding insulating discs and equipotential lids, are moved by the transport belt 3 through the high frequency field, in the direction of the arrow 7. The furnace is shielded by, and enclosed in, a housing 8 in order to avoid sweep radiation. The housing 8 has bilaterally open portions 9a and 9b of specific dimensions and design. If the furnace includes only the high potential electrode 1 and the transport belt electrode 3, and excludes the auxiliary electrodes of the invention, the field intensity has the characteristic illustrated in FIG. la. As shown in FIG. la, the field intensity reaches its maximum shortly after the start of the high frequency field. This produces an intensive heating of the material being processed, which intensive heating is frequently undesired, as hereinbefore indicated, since it may result in adverse conditions in the material being processed.

In each of FIGS. la, lb and 1c, the abscissa represents the length L in meters and the ordinate represents the field intensity in Volts per centimeter.

In accordance with the invention, a plurality of auxiliary electrodes 10, 11, I2 and 13 are positioned between the material to be processed and the high potential electrode 1 in order to control the field intensity. The auxiliary electrodes 10, 11, 12 and 13 are positioned either in grounded or insulated relation and may be heated from within up to approximately 100 C. by an infrared radiator. The auxiliary electrodes 10, 11, 12 and 13 are positioned in parallel relation with each other, so that they are the equivalent of the rungs of a ladder. The auxiliary electrodes 10, 11, I2 and 13 are mounted or supported on a mounting arrangement comprising a support member 14. The support member 14, and therefore the auxiliary electrodes 10, 11, 12 and 13 mounted thereon, may be moved in vertical directions due to the cooperation of adjusting screws and longitudinal bores 15 and 16 formed in the housing. The auxiliary electrodes 10, 11, 12 and 13 may thus be moved, in accordance with operating requirements, to varying heights or levels h from the transport belt electrode 3.

FIG. 3, which is an end view, taken from the left-hand side of FIG. I, discloses another mounting arrangement for varying the distance between the auxiliary electrodes 10, ll, 12 and I3 and the transport belt electrode 3. The mounting arrangement of FIG. 3 comprises a pair of angular supports 17 and 18 which are spaced from each other and each of which has a cooperating adjusting screw provided therein. The angular support 17 thus has an adjusting screw cooperating therewith and the angular support 18 has an adjusting screw 19 cooperating therewith. Each of the adjusting screws 19 and 20 extends through its corresponding angular structure and a longitudinal bore formed through a corresponding one of a pair of cover plates 21 and 22.

The cover plates 21 and 22 are joined by a support member 23 which extends horizontally between them. The support member 23 has notches 24 formed in its upper surface. The auxiliary electrodes 10, ll, 12 and 13 rest in any desired one of the notches 24 of the structural member 23. In this manner, the distances a, b and c (FIG. 3) between adjacent ones of the auxiliary electrodes 10, ll, 12 and 13 may be varied as desired, as well as the height h of said auxiliary electrodes from the transport belt electrode 3.

All the auxiliary electrodes 10, 11, 12 and 13 are grounded in order to provide the field intensity characteristic of FIG. lb. In the field intensity characteristic of FIG. lb, the initial field intensity is considerably lower than the initial field intensity of the characteristic of FIG. la.

If, on the other hand, the auxiliary electrodes 10, 12 and 13, or another suitable group of said auxiliary electrodes, are grounded, the field intensity characteristic of FIG. 10 is provided. In the field intensity characteristic of FIG. 10, after the initial weak field intensity, there is a sudden upsurge of field intensity. In order to obtain the field intensity characteristic of FIG. 10, the auxiliary electrode 11 is mounted in electrical insulation from the other auxiliary electrodes and causes the increase in the field intensity.

Any desired field intensity characteristic may be provided by an appropriate arrangement of the auxiliary electrodes 10, 11, 12 and 13. Thus, for example, an alternate arrangement of grounded and insulated auxiliary electrodes will produce a sawtooth field intensity characteristic, and a pulse type field will act upon the material being processed.

Each of the auxiliary electrodes 10, ll, 12 and 13 may comprise a solid copper rod or a hollow copper tube or pipe. If the auxiliary electrodes are copper tubes, the heating elements which heat the auxiliary electrodes may be positioned in the interior of said tubes. If the auxiliary electrodes are copper rods, they have to be heated by outside radiation. If necessary, the auxiliary electrodes 10, 11, 12 and 13 may also be coated with a layer of electrical insulation. such as, for example, a varnish or plastic.

FIG. 4 is a cross-sectional view of an auxiliary electrode having an elliptical cross-sectional area. The auxiliary electrode of FIG. 4 is of hollow tubular configuration and may be rotated about either axis of the ellipse. The broken lines in FIG. 4 illustrate the rotation of the auxiliary electrode about one of its axes 25. The rotation of the auxiliary electrode about one of its axes, permits a precision adjustment of the field intensity.

FIG. 5 illustrates an auxiliary electrode having the configuration of a plate. The auxiliary electrode of FIG. 5 may be rotated about its axis 26 or the other of its axes perpendicular to said axis. The cross-sectional area of the auxiliary electrode of FIG. 5 is rectangular and the edges are rounded off, to eliminate any point effect.

The auxiliary electrodes 10, ll, 12 and 13 are nonnally positioned transversely to the longitudinal axis 28 (FIG. 1) of the furnace. As shown in FIG. 2, each of the auxiliary electrodes has a length which is greater than the width of the high potential electrode 1. In other words, each of the auxiliary electrodes 10, 11, 12 and 13 extends beyond the high potential electrode 1 at both ends thereof. This results in the catching of most of the stray field.

The auxiliary electrodes 10, 11, 12 and 13 may also be positioned parallel to the longitudinal axis 28 of the furnace, or at an acute angle therewith. The length of each of the auxiliary electrodes may then be less than the width of the high potential electrode.

It is obvious, of course, that our invention is not limited to the examples illustrated, but may be utilized in many different arrangements. It is possible, in accordance with our invention, to automatically adjust the auxiliary electrodes in accordance with a predetermined field intensity curve, that is, in accordance with a predetermined program. Furthermore, the apparatus of our invention is not limited to processing spools, spindles or spinning cakes, but may be utilized in any circumstances in which a sudden vapor development or sudden overheating is to be avoided. Such developments occur, for example, during the drying of casting cores, and in high frequency drying systems for sugar and the like.

While the invention has been described by means of specific examples and in specific embodiments, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

We claim:

l. A capacitive high frequency continuous heating furnace for processing material passing through the furnace along a travel path on a transport belt between a high potential electrode and a grounded electrode, said furnace comprising auxiliary electrodes between the high potential electrode and the material to be processed for adjusting the field intensity between the high potential electrode and the grounded electrode along the travel path of the material to be processed, and means for applying to said auxiliary electrodes a potential which deviates from the potential of the high potential electrode.

2. A furnace as claimed in claim 1, wherein the means for applying a potential to the auxiliary electrodes connects at least a number of the auxiliary electrodes positioned at the beginning of the travel path of the material to be processed to a point at ground potential.

3. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are rods positioned transversely to the longitudinal axis of said furnace.

4. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are rods positioned parallel to the longitudinal axis of said furnace.

5. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are tubes positioned transversely to the longitudinal axis of said furnace.

- 6. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are plates positioned transversely to the longitudinal axis of said furnace. 7. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said high potential electrode has a specific width and said auxiliary electrodes are positioned transversely to the longitudinal axis of said furnace and each of said auxiliary electrodes has a length which is greater than the width of said high potential electrode.

8. A furnace as claimed in claim 1, wherein said auxiliary electrodes are parallel to each other.

9. A furnace as claimed in claim 1, further comprising mounting means for mounting said auxiliary electrodes in a manner whereby the distance between adjacent auxiliary electrodes is variable and the distance of said auxiliary electrodes from said grounded electrode is variable. 

1. A capacitive high frequency continuous heating furnace for processing material passing through the furnace along a travel path on a transport belt between a high potential electrode and a grounded electrode, said furnace comprising auxiliary electrodes between the high potential electrode and the material to be processed for adjusting the field intensity between the high potential electrode and the grounded electrode along the travel path of the material to be processed, and means for applying to said auxiliary electrodes a potential which deviates from the potential of the high potential electrode.
 2. A furnace as claimed in claim 1, wherein the means for applying a potential to the auxiliary electrodes connects at least a number of the auxiliary electrodes positioned at the beginning of the travel path of the material to be processed to a point at ground potential.
 3. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are rods positioned transversely to the longitudinal axis of said furnace.
 4. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are rods positioned parallel to the longitudinal axis of said furnace.
 5. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliaRy electrodes are tubes positioned transversely to the longitudinal axis of said furnace.
 6. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said auxiliary electrodes are plates positioned transversely to the longitudinal axis of said furnace.
 7. A furnace as claimed in claim 1, wherein the furnace houses said high potential electrode, said grounded electrode, said auxiliary electrodes and said material to be processed and has a longitudinal axis, and wherein said high potential electrode has a specific width and said auxiliary electrodes are positioned transversely to the longitudinal axis of said furnace and each of said auxiliary electrodes has a length which is greater than the width of said high potential electrode.
 8. A furnace as claimed in claim 1, wherein said auxiliary electrodes are parallel to each other.
 9. A furnace as claimed in claim 1, further comprising mounting means for mounting said auxiliary electrodes in a manner whereby the distance between adjacent auxiliary electrodes is variable and the distance of said auxiliary electrodes from said grounded electrode is variable. 